The authors would like to thank Theresa Jones, Ph.D. for her guidance and assistance in adapting the reaching task to mice. Data presented in this manuscript were supported by grants from NIH-NINDS (NS64586 to TAJ and NS076275 to ALK) and a predoctoral NRSA to KAT (F31AG034032). The NIH was not involved in any aspect of study designs or analyses presented in this manuscript nor in the composition of this manuscript.

The following methods are in accordance with protocols approved by the University of Texas at Austin and Illinois Wesleyan Animal Care and Use Committees.&#160;It is recommended that researchers either wear gloves or take appropriate precautions (washing hands before and after) when engaging in behavioral training with any laboratory animal. Gloves must be worn when handling animals in preparation for and during surgery.
1. Habituation and Food Restriction
NOTE: As the PMRT is an appetitive task, it is beneficial to restrict the amount and timing of feeding prior to the onset of training in order to motivate the reaching response and prevent satiety during training sessions.
<ol>
	<li>Place mice on a restricted feeding schedule beginning at least 1 week prior to the onset of task training. Weigh each mouse prior to the onset of food restriction to establish free-feeding weights, which are determined as the weights of each animal on the first day of restricted feeding.
	<ol>
		<li>Feed mice once daily, with each mouse receiving ~2.5 g of standard rodent chow per day (e.g., if there are 4 mice housed in a cage, the cage will receive 10 g of food daily). Ensure feeding occurs at the same time each day, preferably at the time daily training sessions are expected to conclude.</li>
		<li>Weigh animals regularly to ensure that no mouse loses more than 10% of their free-feeding weight. NOTE: Adjust daily food amounts accordingly to promote appropriate weight maintenance. Mice typically gain weight as they mature, even with constant food restriction Mice remain on food restriction for the duration of PMRT training/assessment.</li>
	</ol>
	</li>
	<li>Expose animals to smaller pieces of pasta (cut to 1.6 cm) in their home cage several times prior to training in order to overcome neophobic responses. NOTE: Typically 5-10 days of exposure are sufficient, with about 4 pieces per mouse provided at each feeding.</li>
	<li>Cut pasta pieces to size (3.2 cm) using a razor blade. NOTE: It is recommended that an excess of pasta pieces are cut prior to beginning the day&#8217;s training and unused pieces stored in an airtight container. Capellini pasta is used to fill the matrix. As different brands of pasta vary in texture and diameter, which could influence the stability of pasta in the matrix or the amount of force necessary for the mice to break the pasta, it is recommended that DeCecco brand pasta be used throughout training and testing.</li>
	<li>Place uncooked capellini pasta pieces in the pasta matrix, filling all available holes in the matrix (Figure 1A).</li>
	<li>Habituate mice to the testing chamber with a full pasta matrix placed in front (Figure 1A) and several pieces of pasta to eat at the bottom of the testing chamber. Habituate mice for 3 sessions of 5-10 min. NOTE: Mice should not be encouraged to reach for pasta during habituation training. Mice usually begin to show interest in the pasta located outside of the reaching chamber by sniffing at it through the aperture. It is possible to habituate two cage mates in a single chamber if desired, but mice should be shaped and trained individually.&#160;All surfaces should be cleaned with 70% ethanol or a similar, safe disinfecting solution before and after each animal is placed in the behavioral apparatus.</li>
</ol>
2. Shaping the Reach
<ol>
	<li>Determine each animal&#8217;s preferred limb by shaping the reach over 3-5 once-daily shaping trials. Permit mice to reach for 10 min or a total of 10 times, which occurs first.
	<ol>
		<li>Place mice individually in the testing chamber with a full pasta matrix in front of the chamber as in habituation training (Figure 1A).</li>
		<li>Record the number of reaches with each limb, denoting the number of reaches with the right and left limbs separately. Define a reach as extension of the limb through the reaching aperture such that the wrist breaks the plane of the chamber; it is not necessary for the reach to be directed toward or make contact with the pasta.</li>
	</ol>
	</li>
	<li>Hold several pieces of pasta just inside the chamber through the reaching aperture to encourage mice that are reluctant to reach. Draw the pasta pieces out when the mouse shows interest (e.g. sniffing, biting), thus encouraging them to reach after the retreating pasta pieces. If the mice do not initially show interest in the dry pasta, then wet the tips of the pasta pieces in a small cup of warm water to make them more palatable.</li>
	<li>Determine limb preference when a mouse exhibits a minimum of 70% of their daily reaches with a single limb. Do not to over-shape animals, as this can limit the amount of learning observed during the training portion of reaching tasks 17. Begin PMRT training once mice are shaped. NOTE: Training can be started as soon as the next day, but it is also acceptable to wait several days between shaping and training procedures.</li>
</ol>
3. Reaching Training
<ol>
	<li>Train mice once daily prior to insult in order to establish proficiency on the PMRT. NOTE: Each trial consists of a maximum of 15 min or 100 reaches counted by the observer&#160;(successful and unsuccessful), whichever occurs first. Mice are trained to reach only with their preferred limb. Mice will tolerate two trials per day if a more intense training paradigm is desired 18.
	<ol>
		<li>Place mice in the testing chamber with a half-full matrix placed in front (Figure 1B). Train mice to reach only with their preferred limb by filling only the side of the matrix contralateral to the preferred limb since mice reach across the midline of their body. Leave the portion of the matrix corresponding to the unpreferred limb unfilled in order to discourage reach attempts with this limb (which would not be successful because they cannot reach the pasta) and encourage reaching only with the preferred limb.</li>
	</ol>
	</li>
	<li>Place a small amount of pressure on the pasta while it is in the matrix to help mice successfully break pieces during early training sessions. Do not break the pasta pieces for the mouse. Achieve this by holding one or two pasta pieces lightly behind and perpendicular to the intended reaching target. This small amount of support helps stabilize the thin pasta, which is quite flexible and difficult for mice to grasp as they are initially learning the task.</li>
	<li>Record the total number of reaches, number of successful reaches, and locations of successful reaches. Successful reaches require the mouse to reach through the aperture, grab a piece of pasta, and break the pasta piece to remove it from the matrix. NOTE: Pasta pieces should not be replaced in the matrix until after the trial has terminated. Early in training, mice will not break many pasta pieces.</li>
	<li>Train mice on the PMRT to proficiency, which is defined as at least 3 days (and up to 5 days) of consistent performance (breaking at least 9 pieces of pasta with no more than 2 more or fewer pieces over days). It often takes between 15-20 days to train young adult mice to proficiency.</li>
</ol>
4. Less-affected Limb Training
<ol>
	<li>Train the less-affected limb (i.e., the pre-operative unpreferred limb) beginning four days after ischemic insult to the motor cortex contralateral to the preferred reaching limb (see Figure 2 for clarification on affected/preferred and less-affected/unpreferred limbs). Administer once daily 15-min or 100-reach training sessions.
	<ol>
		<li>Remove the first column of pasta (i.e., the most medial vertical column extending from the reaching aperture) for the first week of less-affected limb training in order to ensure that early reaches with the affected limb are not successful.</li>
		<li>Place mice in the reaching chamber with the half-filled matrix placed in front. Ensure that the filled half of the matrix is opposite of the pre-operative filled half, which will force the mice to now reach with the less-affected (unpreferred) limb.</li>
	</ol>
	</li>
	<li>Encourage reaching with the less-affected limb by reinforcing extension of this limb through the reaching aperture. When mice extend the less-affected limb in the first few days of training place a small (1/2 piece) of pasta onto the floor of the reaching chamber regardless of whether or not the reach is successful.</li>
	<li>Count only those reaches made with the less-affected limb toward to the 100 reach total. Do not count furtive attempts with the affected limb towards the total number of reaches.</li>
	<li>Return the most medial vertical column of pasta to the matrix after the first 7 days of less-affected limb training.</li>
	<li>Record the number of reaches, number of successful reaches, and locations of successful reaches. NOTE: These data can be analyzed to observe differences in reaching patterns with the less-affected limb, but have not been previously reported.</li>
</ol>
5. Reaching Analysis
Determine the impact of less-affected limb use on recovery of function of the affected limb by assessing the affected limb on the PMRT task following less-affected limb training. This assessment occurs after the desired number of less-affected limb training days are complete (typically 14 days).
<ol>
	<li>Place the matrix in front of the chamber, oriented identically to training procedures (i.e., with the half of the matrix contralateral to the preferred limb filled). NOTE: This forces mice to reach with their affected (and previously preferred) limb.</li>
	<li>Record the total number of reaches, number of successful reaches, and locations of successful reaches to compare with pre-stroke performance levels. Do not probe performance of the affected limb during less-affected limb training as these affected limb probes may function as training sessions that could impact recovery of the affected limb.</li>
</ol>

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The authors have nothing to disclose.

The PMRT represents a simple, quantitative way to assess skilled reaching performance in mice. Though time consuming, it is possible for previously inexperienced undergraduates to be trained to collect reliable and reproducible data with only a few training sessions. The task is sensitive enough to measure even slight changes in mouse motor skill performance following ischemic insult 3, 13, 15, and a number of studies cite long-term deficits with a variety of training protocols 15, 20, 22. Because it is a unilateral task, it can also be used to dictate the limb with which mice perform the task. This feature of the PMRT allows it to be effective in studies of both adaptive behavioral and neural plasticity following insult as well as maladaptive and compensatory changes that occur with learned reliance on the less-affected limb. The task also lends itself to studies of bimanual limb use, which have been investigated in rat models but not presently in the mouse 23.
The most critical aspects of the current protocol include: accurately determining the preferred limb prior to training, training mice to proficiency on the skilled motor task prior to injury, and switching the mice from preferred/affected limb reaching to unpreferred/less-affected limb reaching in the first week of post-operative training. To accurately determine the preferred limb prior to training it is important to allow mice to reach for pasta in the full matrix during shaping. Mice should be encouraged to reach, but they should not be rewarded for reaches, which may unintentionally bias the limb with which they reach. Shaping sessions are not training sessions, and therefore mice should not be specifically encouraged to break pasta pieces, be rewarded for reaching behavior, or reach an excessive number of times per session 3. It is also important that mice acquire the motor skill prior to ischemic insult so that accurate data can be collected regarding the effects of both affected and less-affected limb training after injury, as well as to permit appropriate quantification of initial deficit following injury. A minimum of 15 days of pre-operative training (excluding shaping) is suggested to ensure acquisition on the task. A good rule of thumb is to make sure that animals are consistent in their performance, thus exhibiting a stable performance across at least 3-5 training of days. This can best be accomplished by graphing the pre-operative reaching data for each animal to visually observe success patterns. If performance appears asymptotic over 3-5 days (i.e., varies by less than 2 successful retrievals across days), it is safe to assume that the animal has sufficiently acquired the task. Mice typically reach an asymptotic success level of ~11 pieces, but with extended (months) training can gradually reach success levels of ~14 pieces 24. Finally, especially with relatively small lesions 13, 20, mice may continue to attempt reaching with the affected limb early in less-affected limb training. It is helpful to remove the first column of pasta from the matrix during the first 7 days of less-affected limb training to discourage this behavior. The mice may be able to break the first several pieces of pasta with their affected limb if the full half matrix used, and this success will further encourage affected limb reaching despite an inability to successfully retrieve pieces beyond these first few. During the first week of less-affected limb training, the total number of affected reaches can be quantified, but the number of successful breaks will not be informative. As mentioned above, only successful affected limb reaches are analyzed for data interpretation. To further encourage less-affected limb reaching, it is helpful to provide small (&#189; sized) pasta pieces as rewards for attempted reaches with the less-affected limb. This practice is usually necessary for the first 2-3 days of less-affected limb training, at which point mice become proficient at reaching with the less-affected limb and will begin successfully breaking and retrieving pasta pieces.
Collecting behavioral data with mice can be effective and rewarding, but it is important to remember that mice are not small rats. They have a unique temperament and behavioral repertoire that should be considered for behavioral tasks. Using well-handled, tamed mice increases successful behavioral data collection. Several weeks of regular handling are recommended. In addition, mice sometimes require &#8220;focusing&#8221; during behavioral training. It is helpful to gently brush pasta pieces in the matrix to make a distinct noise that the mice respond to. It may also be helpful to gently brush the inside of the reaching aperture.
The current protocol describes a sensitive behavioral task for the collection of skilled reaching data in mice following small ischemic strokes. Motor impairments are among the most common and chronic consequences of stroke 25, 26, and are therefore the focus of a number of basic science research laboratories (e.g., 27-32). Skilled reaching tasks are the most commonly used tests of dexterous forelimb use in rodents, and have historically been most often used in rat models of injury (e.g., 11, 19, 28, 33), although their use in mouse models is becoming quite frequent 34, 35. The application of skilled reaching tasks in mice, such as the PMRT, allows for improved mouse models of stroke 3 and thus better translational potential of these basic science experiments. Because of their affordability, the available genetic tools, and their prevalence in neurobiological laboratories, mice are important tools in the study of stroke mechanisms and recovery. The availability of behavioral manipulations that sensitively assess motor performance, can be used for rehabilitative strategies, and can mimic human compensatory responses extends the application of the mouse model. The methods described in this protocol can certainly be further refined and extended to other mouse injury models, including traumatic brain injury, studies of bimanual limb use following insult and studies of neural mechanisms that sub serve and support functional recovery.

Mouse models have become increasingly popular for experimental stroke research due in part to their convenience and affordability, as well as the availability of transgenic lines that are suitable for in vivo imaging among other applications. With this increased popularity in experimental models, the interest in developing sensitive behavioral assessments of functional outcome following injury has also increased 1-7. The development of animal training protocols that mimic both rehabilitation and compensatory strategies used by human stroke survivors improves the ability to successfully translate findings from experimental animal studies to use in the clinic 8. Motor skill training on the Pasta Matrix Reaching Task (PMRT) has been previously established as a sensitive behavioral assessment of motor skill outcome following ischemic insult of the sensorimotor cortex 3.
One of the primary interests in stroke research concerns rehabilitation and the development and understanding of behavioral strategies that promote improved recovery of function following insult. Currently, rehabilitation strategies in humans result in incomplete recovery 8. In addition, rehabilitation therapists must combat compensatory strategies that stroke survivors develop during recovery that may undermine their ability to fully regain function of their affected limb(s). For example, following a unilateral stroke that affects upper extremity function, humans tend to develop a reliance on their less-affected limb 9, 10. While improving a person&#8217;s ability to function in the short term, this learned non-use of the affected limb may impede its ultimate recovery potential, as demonstrated in animal models 11-13. These findings in animals have helped to inform the development and use of constraint-induced movement therapy in humans 14. Animal models are beneficial for improving rehabilitation strategies by allowing researchers to explore the neurobiological mechanisms that subserve and promote recovery of function. In addition to being an effective behavioral assessment of post-stroke function, the PMRT has been established as an effective rehabilitative strategy to promote improved functional outcome following sensorimotor stroke 15. The PMRT can also be used to effectively mimic learned non-use of the affected limb and therefore offer insight into behavioral manipulations that may improve functional recovery despite initial over-reliance on the less-affected limb 13.
Construction of the PMRT has been described previously 3. Briefly, the reaching chamber is composed of four Plexiglas walls (20 cm tall, 15 cm long, and 8.5 cm wide) with an open top and bottom. There is a center slit (13 cm tall and 5 mm wide) extending from the bottom base of the front wall of the chamber that serves as the reaching aperture (Figure 1A). The pasta matrix is a heavy-duty plastic block (8.5 cm long, 5 cm wide, and 1.5 cm tall) with 1 mm diameter holes drilled completely through the depth of the block. There are a total of 260 holes, beginning 2 mm from the reaching window with 2 mm between each hole (Figure 1B). The pasta matrix is designed such that dry, vertically oriented pasta pieces extend through the entire depth of the matrix stage with approximately half of the pasta piece exposed. A removable piece of overhead plastic or cardstock should be cut to size and taped securely to the underside of the matrix. This prevents the pasta pieces from falling out of the matrix during transport and allows for easy removal of broken pasta pieces.
The PMRT is a versatile and sensitive behavioral assay that permits experimenters to collect accurate outcome data and manipulate limb use to mimic clinical phenomena. As a behavioral outcome measure, the PMRT allows experimenters to collect behavioral data that more accurately reflect the effectiveness of a rehabilitative strategy than does the traditional measure of infarct size 3, 16. As a behavioral manipulation, the PMRT allows experimenters to control upper limb use in mice in order to mimic clinical experiences of rehabilitation (i.e. affected limb training) or learned non-use (i.e. less-affected limb training). When combined with neuroanatomical methods, the PMRT provides researchers with an opportunity to explore the mechanisms that support behavioral recovery of function or maladaptive plasticity following compensatory limb use after stroke. The PMRT could be further applied to other murine models of brain injury and upper extremity impairment, such as traumatic brain injury. Another advantage of the PMRT is its affordability. The equipment required for the task can be constructed fairly reasonably in house, data collection does not require a large amount of space or financial resources, and the task is simple enough for undergraduate students to reliably collect data. Further, the PMRT is sensitive to even small behavioral deficits 3, 13. This protocol provides a simple and effective way to assess motor skill learning, promote behavioral recovery following injury, and mimic learned non-use phenomena in an established murine model of stroke.

<table border="0" cellpadding="0" cellspacing="0" width="794">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Name of Material/ Equipment</td>
			<td style="width:71px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:388px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Reaching Chamber</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>Reaching chambers are made in house with Plexiglas</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Pasta Matrix Block</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>The Pasta Matrix box is made in house using a heavy plastic block</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Capellini Pasta</td>
			<td style="width:71px;">DeCecco</td>
			<td style="width:119px;"></td>
			<td style="width:388px;">DeCecco brand capellini pasta can be purchased in a grocery store or through an online retailer such as Amazon</td>
		</tr>
	</tbody>
</table>

compensatory limb use and behavioral assessment of motor skill learning following sensorimotor cortex injury in a mouse model of ischemic stroke

Mouse models have become increasingly popular in the field of behavioral neuroscience, and specifically in studies of experimental stroke. As models advance, it is important to develop sensitive behavioral measures specific to the mouse. The present protocol describes a skilled motor task for use in mouse models of stroke. The Pasta Matrix Reaching Task functions as a versatile and sensitive behavioral assay that permits experimenters to collect accurate outcome data and manipulate limb use to mimic human clinical phenomena including compensatory strategies (i.e., learned non-use) and focused rehabilitative training. When combined with neuroanatomical tools, this task also permits researchers to explore the mechanisms that support behavioral recovery of function (or lack thereof) following stroke. The task is both simple and affordable to set up and conduct, offering a variety of training and testing options for numerous research questions concerning functional outcome following injury. Though the task has been applied to mouse models of stroke, it may also be beneficial in studies of functional outcome in other upper extremity injury models.

The results from PMRT analysis should include the number of pasta pieces broken and the pattern of successful reaches. Results from mice with sensorimotor cortical lesions indicate that ischemic insult affects both the number of successful reaches as well as physical reach patterns 3, 19, as demonstrated in Figure 3A. Representative pattern changes can be observed in Figure 3B. The ability of the PMRT to mimic learned non-use effects in mice is demonstrated by impaired recovery of the affected limb following less-affected limb training 13, 20. As a result, only successful reaches with the affected limb are analyzed. Results from mice with ischemic lesions to the sensorimotor cortex suggest that two weeks of less-affected limb training following ischemic stroke impairs affected limb use for at least seven days 13. As demonstrated in Figure 4, mice that receive less-affected limb training for 15 days after unilateral ischemic insult exhibit fewer successful reach attempts over seven days of affected limb assessment. Mice that receive no training (control) for 15 days following stroke recover the ability to successfully retrieve pasta pieces with seven days of affected limb assessment. This effect has been found to persist with up to 28 days of subsequent affected limb assessment following less-affected training 20.
The PMRT could also be used to assess qualitative changes in reaching as has been studied in rats with the single pellet reaching task 21. This assessment, which has yet to be conducted in mice, would require the systematic analysis of videotaped reaches in the PRMT.
<img alt="Figure 1" fo:content-width="5in" src="/files/ftp_upload/51602/51602fig1highres.jpg" width="500" /> 
Figure 1. Pasta matrix reaching task materials. The PMRT requires a rectangular box (20 cm tall, 15 cm long, and 8.5 cm wide) with a 13 mm high, 5 mm wide reaching aperture (indicated by arrow) in the center of one wall. The matrix consists of a heavy-duty plastic block (8.5 cm long, 5 cm wide, and 1.5 cm tall) with 260 1 mm holes drilled 2 mm apart. Dry capellini pasta (3.2 cm long) is oriented vertically in the block (A). During shaping, the entire matrix is filled with pasta. However, during skilled reach training of the affected or less-affected limb only half of the matrix is filled. This requires the mouse to reach across the body with a single limb (e.g., the preferred limb during pre-operative training) (B). The present images are reprinted with permission 3.
<img alt="Figure 2" fo:content-width="5in" src="/files/ftp_upload/51602/51602fig2highres.jpg" width="500" /> 
Figure 2. Affected and less-affected limbs. The PMRT can be manipulated to engage either the affected or the less-affected limb. Solid black coloring indicates Preferred/affected limbs in the first two images and the less-affected limb in the third image. This graphic helps to demonstrate the affected and less-affected limbs in reference to the preferred limb.
<img alt="Figure 3" fo:content-width="5in" src="/files/ftp_upload/51602/51602fig3highres.jpg" width="500" /> 
Figure 3. Representative reaching patterns with the affected limb. Reaching patterns of mice both before and after unilateral ischemic insult of the sensorimotor cortex opposite the preferred limb are presented (A). Anterior denotes pasta pieces located increasingly further in front of the mouse, while lateral denotes pasta pieces located increasingly to the side of the mouse. Representative pattern changes can be observed in B. With focused training of the affected limb, reach trajectory and success improve. This figure is reprinted with permission 3.
<img alt="Figure 4" fo:content-width="5in" src="/files/ftp_upload/51602/51602fig4highres.jpg" width="500" /> 
Figure 4. Representative results of less-affected limb training on affected limb outcome. Training of the less-affected limb for 15 days following unilateral ischemic insult of the sensorimotor cortex impairs functional outcome of the affected limb, preventing functional recovery. This figure is reprinted with permission 13.

Watch this Scientific Journal Video about Compensatory Limb Use and Behavioral Assessment of Motor Skill Learning Following Sensorimotor Cortex Injury in a Mouse Model of Ischemic Stroke at JoVE.com

Compensatory Limb Use and Behavioral Assessment of Motor Skill Learning Following Sensorimotor Cortex Injury in a Mouse Model of Ischemic Stroke

Mouse models have become increasingly popular in studies of behavioral neuroscience. As models advance, it is important to develop sensitive behavioral measures specific to the mouse. This protocol describes the Pasta Matrix Reaching Task, which is a skilled motor task for use in mouse models of stroke.

Mouse models have become increasingly popular in the field of behavioral neuroscience, and specifically in studies of experimental stroke. As models ...

compensatory-limb-use-behavioral-assessment-motor-skill-learning

Nanyang Technological University

Research

JoVE Journal

Behavior

11.4K Views.  Illinois Wesleyan University. Mouse models have become increasingly popular in studies of behavioral neuroscience. As models advance, it is important to develop sensitive behavioral measures specific to the mouse. This protocol describes the Pasta Matrix Reaching Task, which is a skilled motor task for use in mouse models of stroke.

Video: Compensatory Limb Use and Behavioral Assessment of Motor Skill Learning Following Sensorimotor Cortex Injury in a Mouse Model of Ischemic Stroke

Assessment of Sensorimotor Function in Mouse Models of Parkinson's Disease

Sensitive and reliable behavioral outcome measures are essential to the evaluation of potential therapeutic treatments in preclinical trials for many neurodegenerative diseases. In Parkinson's disease, sensorimotor tests sensitive to varying degrees of nigrostriatal dysfunction are fundamental for testing the efficacy of potential therapeutics. Reliable and quite elegant sensorimotor measures exist for rats, however many of these tests measure sensorimotor asymmetry within the rat and are not entirely suitable for the newer genetic mouse models of PD. We have put together a battery of sensorimotor tests inspired by the sensitive tests in rats and adapted for mice. The test battery highlighted in this study is chosen for a) its sensitivity in a wide variety of mouse models of PD, b) its ease in implementing into a study, and c) its low expense. These tests have proven useful in characterizing novel genetic mouse models of PD as well as in testing potential disease-modifying therapies.

In Parkinson's disease and movement disorders in general, sensitive and reliable behavioral assays are essential for testing novel potential therapeutics. Here, we describe a manageable battery of sensorimotor tests for mice that are sensitive to varying degrees of injury to the nigrostriatal system and useful for preclinical studies.

Sensitive and  reliable behavioral outcome measures are essential to the evaluation of  potential therapeutic treatments in preclinical trials for many  ...

Study Motor Skill Learning by Single-pellet Reaching Tasks in Mice

Reaching for and retrieving objects require precise and coordinated motor movements in the forelimb. When mice are repeatedly trained to grasp and retrieve food rewards positioned at a specific location, their motor performance (defined as accuracy and speed) improves progressively over time, and plateaus after persistent training. Once such reaching skill is mastered, its further maintenance does not require constant practice. Here we introduce a single-pellet reaching task to study the acquisition and maintenance of skilled forelimb movements in mice. In this video, we first describe the behaviors of mice that are commonly encountered in this learning and memory paradigm, and then discuss how to categorize these behaviors and quantify the observed results. Combined with mouse genetics, this paradigm can be utilized as a behavioral platform to explore the anatomical underpinnings, physiological properties, and molecular mechanisms of learning and memory.

Persistent practice improves the precision of coordinated movements.&#160;Here we introduce a single-pellet reaching task, which is designed to assess the learning and memory of forelimb skill in mice.&#160;

Reaching for and retrieving objects require precise and coordinated motor movements in the forelimb. When mice are repeatedly trained to grasp and ...

Behavioral Assessment of the Aging Mouse Vestibular System

Age related decline in balance performance is associated with deteriorating muscle strength, motor coordination and vestibular function. While a number of studies show changes in balance phenotype with age in rodents, very few isolate the vestibular contribution to balance under either normal conditions or during senescence. We use two standard behavioral tests to characterize the balance performance of mice at defined age points over the lifespan: the rotarod test and the inclined balance beam test. Importantly though, a custom built rotator is also used to stimulate the vestibular system of mice (without inducing overt signs of motion sickness). These two tests have been used to show that changes in vestibular mediated-balance performance are present over the murine lifespan. Preliminary results show that both the rotarod test and the modified balance beam test can be used to identify changes in balance performance during aging as an alternative to more difficult and invasive techniques such as vestibulo-ocular (VOR) measurements.

Motor control and balance performance are known to deteriorate with age. This paper presents a number of standard noninvasive behavioral tests with the addition of a simple rotary stimulus to challenge the vestibular system and show changes in balance performance in a murine model of aging.

Age related decline in balance performance is associated with deteriorating muscle strength, motor coordination and vestibular function. While a number of ...

Experimental Assessment of Mouse Sociability Using an Automated Image Processing Approach

Mouse is the preferred model organism for testing drugs designed to increase sociability. We present a method to quantify mouse sociability in which the test mouse is placed in a standardized apparatus and relevant behaviors are assessed in three different sessions (called session I, II, and III).
The apparatus has three compartments (see Figure 1), the left and right compartments contain an inverted cup which can house a mouse (called &#34;stimulus mouse&#34;).
In session I, the test mouse is placed in the cage and its mobility is characterized by the number of transitions made between compartments. In session II, a stimulus mouse is placed under one of the inverted cups and the sociability of the test mouse is quantified by the amounts of time it spends near the cup containing the enclosed stimulus mouse vs. the empty inverted cup. In session III, the inverted cups are removed and both mice interact freely. The sociability of the test mouse in session III is quantified by the number of social approaches it makes toward the stimulus mouse and by the number of times it avoids a social approach by the stimulus mouse.
The automated evaluation of the movie detects the nose of the test mouse, which allows the determination of all described sociability measures in session I and II (in session III, approaches are identified automatically but classified manually). To find the nose, the image of an empty cage is digitally subtracted from each frame of the movie and the resulting image is binarized to identify the mouse pixels. The mouse tail is automatically removed and the two most distant points of the remaining mouse are determined; these are close to nose and base of tail. By analyzing the motion of the mouse and using continuity arguments, the nose is identified.
<img alt="Figure 1" src="/files/ftp_upload/52508/52508fig1.jpg" /> 
Figure 1. Assessment of Sociability During 3 sessions. Session I (top): Acclimation of test mouse to the cage. Session II (middle): Test mouse moving freely in the cage while the stimulus mouse is enclosed in an inverted cup. Session III (bottom): Both test mouse and stimulus mouse are allowed to move freely and interact with each other.

This protocol describes a method to quantify mouse sociability. Mice are videotaped as they move and interact in a special cage. Movie processing allows for the automated quantification of sociability with excellent accuracy and reliability.

Mouse is the preferred model organism for testing drugs designed to increase sociability. We present a method to quantify mouse sociability in which the ...

Combined Shuttle-Box Training with Electrophysiological Cortex Recording and Stimulation as a Tool to Study Perception and Learning

Shuttle-box avoidance learning is a well-established method in behavioral neuroscience and experimental setups were traditionally custom-made; the necessary equipment is now available by several commercial companies. This protocol provides a detailed description of a two-way shuttle-box avoidance learning paradigm in rodents (here Mongolian gerbils; Meriones unguiculatus) in combination with site-specific electrical intracortical microstimulation (ICMS) and simultaneous chronical electrophysiological in vivo recordings. The detailed protocol is applicable to study multiple aspects of learning behavior and perception in different rodent species.
Site-specific ICMS of auditory cortical circuits as conditioned stimuli here is used as a tool to test the perceptual relevance of specific afferent, efferent and intracortical connections. Distinct activation patterns can be evoked by using different stimulation electrode arrays for local, layer-dependent ICMS or distant ICMS sites. Utilizing behavioral signal detection analysis it can be determined which stimulation strategy is most effective for eliciting a behaviorally detectable and salient signal. Further, parallel multichannel-recordings using different electrode designs (surface electrodes, depth electrodes, etc.) allow for investigating neuronal observables over the time course of such learning processes. It will be discussed how changes of the behavioral design can increase the cognitive complexity (e.g. detection, discrimination, reversal learning).

Shuttle-box avoidance learning is well-established in behavioral neuroscience. This protocol describes how shuttle-box learning in rodents can be combined with site-specific electrical intracortical microstimulation (ICMS) and simultaneous chronical in vivo recordings as a tool to study multiple aspects of learning and perception.

Shuttle-box avoidance learning is a well-established method in behavioral neuroscience and experimental setups were traditionally custom-made; the ...

Vagus Nerve Stimulation as a Tool to Induce Plasticity in Pathways Relevant for Extinction Learning

Extinction describes the process of attenuating behavioral responses to neutral stimuli when they no longer provide the reinforcement that has been maintaining the behavior. There is close correspondence between fear and human anxiety, and therefore studies of extinction learning might provide insight into the biological nature of anxiety-related disorders such as post-traumatic stress disorder, and they might help to develop strategies to treat them. Preclinical research aims to aid extinction learning and to induce targeted plasticity in extinction circuits to consolidate the newly formed memory. Vagus nerve stimulation (VNS) is a powerful approach that provides tight temporal and circuit-specific release of neurotransmitters, resulting in modulation of neuronal networks engaged in an ongoing task. VNS enhances memory consolidation in both rats and humans, and pairing VNS with exposure to conditioned cues enhances the consolidation of extinction learning in rats. Here, we provide a detailed protocol for the preparation of custom-made parts and the surgical procedures required for VNS in rats. Using this protocol we show how VNS can facilitate the extinction of conditioned fear responses in an auditory fear conditioning task. In addition, we provide evidence that VNS modulates synaptic plasticity in the pathway between the infralimbic (IL) medial prefrontal cortex and the basolateral complex of the amygdala (BLA), which is involved in the expression and modulation of extinction memory.

Vagus nerve stimulation (VNS) has emerged as a tool to induce targeted synaptic plasticity in the forebrain to modify a range of behaviors. This protocol describes how to implement VNS to facilitate the consolidation of fear extinction memory.

Extinction describes the process of attenuating behavioral responses to neutral stimuli when they no longer provide the reinforcement that has been ...

Investigating Motor Skill Learning Processes with a Robotic Manipulandum

Skilled reaching tasks are commonly used in studies of motor skill learning and motor function under healthy and pathological conditions, but can be time-intensive and ambiguous to quantify beyond simple success rates. Here, we describe the training procedure for reach-and-pull tasks with ETH Pattus, a robotic platform for automated forelimb reaching training that records pulling and hand rotation movements in rats. Kinematic quantification of the performed pulling attempts reveals the presence of distinct temporal profiles of movement parameters such as pulling velocity, spatial variability of the pulling trajectory, deviation from midline, as well as pulling success. We show how minor adjustments in the training paradigm result in alterations in these parameters, revealing their relation to task difficulty, general motor function or skilled task execution. Combined with electrophysiological, pharmacological and optogenetic techniques, this paradigm can be used to explore the mechanisms underlying motor learning and memory formation, as well as loss and recovery of function (e.g. after stroke).

A paradigm is presented for training and analysis of an automated skilled reaching task in rats. Analysis of pulling attempts reveals distinct subprocesses of motor learning.

Skilled reaching tasks are commonly used in studies of motor skill learning and motor function under healthy and pathological conditions, but can be ...

Using a Split-belt Treadmill to Evaluate Generalization of Human Locomotor Adaptation

Understanding the mechanisms underlying locomotor learning helps researchers and clinicians optimize gait retraining as part of motor rehabilitation. However, studying human locomotor learning can be challenging. During infancy and childhood, the neuromuscular system is quite immature, and it is unlikely that locomotor learning during early stages of development is governed by the same mechanisms as in adulthood. By the time humans reach maturity, they are so proficient at walking that it is difficult to come up with a sufficiently novel task to study de novo locomotor learning. The split-belt treadmill, which has two belts that can drive each leg at a different speed, enables the study of both short- (i.e., immediate) and long-term (i.e., over minutes-days; a form of motor learning) gait modifications in response to a novel change in the walking environment. Individuals can easily be screened for previous exposure to the split-belt treadmill, thus ensuring that all experimental participants have no (or equivalent) prior experience. This paper describes a typical split-belt treadmill adaptation protocol that incorporates testing methods to quantify locomotor learning and generalization of this learning to other walking contexts. A discussion of important considerations for designing split-belt treadmill experiments follows, including factors like treadmill belt speeds, rest breaks, and distractors. Additionally, potential but understudied confounding variables (e.g., arm movements, prior experience) are considered in the discussion.

We describe a protocol for investigating human locomotor adaptation using the split-belt treadmill, which has two belts that can drive each leg at a different speed. We specifically focus on a paradigm designed to test the generalization of adapted locomotor patterns to different walking contexts (e.g., gait speeds, walking environments).

Understanding the mechanisms underlying locomotor learning helps researchers and clinicians optimize gait retraining as part of motor rehabilitation. ...

Detecting Behavioral Deficits in Rats After Traumatic Brain Injury

With the increasing incidence of traumatic brain injury (TBI) in both civilian and military populations, TBI is now considered a chronic disease; however, few studies have investigated the long-term effects of injury in rodent models of TBI. Shown here are behavioral measures that are well-established in TBI research for times early after injury, such as two weeks, until two months. Some of these methods have previously been used at later times after injury, up to one year, but by very few laboratories. The methods demonstrated here are a short neurological assessment to test reflexes, a Beam-Balance to test balance, a Beam-Walk to test balance and motor coordination, and a working memory version of the Morris water maze that can be sensitive to deficits in reference memory. Male rats were handled and pre-trained to neurological, balance, and motor coordination tests prior to receiving parasagittal fluid percussion injury (FPI) or sham injury. Rats can be tested on the short neurological assessment (neuroscore), the beam-balance, and the Beam-Walk multiple times, while testing on the water maze can only be done once. This difference is because rats can remember the task, thus confounding the results if repeated testing is attempted in the same animal. When testing from one to three days after injury, significant differences are detected in all three non-cognitive tasks. However, differences in the Beam-Walk task were not detectable at later time points (after 3 months). Deficits were detected at 3 months in the Beam-Balance and at 6 months in the neuroscore. Deficits in working memory were detected out to 12 months after injury, and a deficit in a reference memory first appeared at 12 months. Thus, standard behavioral tests can be useful measures of persistent behavioral deficits after FPI.

The goal of the behavioral tests presented here is to detect functional deficits in rats after traumatic brain injury. Four specific tests are presented that detect deficits in behaviors to reflect the damage to specific brain areas at times extending to one year after injury.

With the increasing incidence of traumatic brain injury (TBI) in both civilian and military populations, TBI is now considered a chronic disease; however, ...

The "Motor" in Implicit Motor Sequence Learning: A Foot-stepping Serial Reaction Time Task

This protocol describes a modified serial reaction time (SRT) task used to study implicit motor sequence learning. Unlike the classic SRT task that involves finger-pressing movements while sitting, the modified SRT task requires participants to step with both feet while maintaining a standing posture. This stepping task necessitates whole body actions that impose postural challenges. The foot-stepping task complements the classic SRT task in several ways. The foot-stepping SRT task is a better proxy for the daily activities that require ongoing postural control, and thus may help us better understand sequence learning in real-life situations. In addition, response time serves as an indicator of sequence learning in the classic SRT task, but it is unclear whether response time, reaction time (RT) representing mental process, or movement time (MT) reflecting the movement itself, is a key player in motor sequence learning. The foot-stepping SRT task allows researchers to disentangle response time into RT and MT, which may clarify how motor planning and movement execution are involved in sequence learning. Lastly, postural control and cognition are interactively related, but little is known about how postural control interacts with learning motor sequences. With a motion capture system, the movement of the whole body (e.g., the center of mass (COM)) can be recorded. Such measures allow us to reveal the dynamic processes underlying discrete responses measured by RT and MT, and may aid in elucidating the relationship between postural control and the explicit and implicit processes involved in sequence learning. Details of the experimental set-up, procedure, and data processing are described. The representative data are adopted from one of our previous studies. Results are related to response time, RT, and MT, as well as the relationship between the anticipatory postural response and the explicit processes involved in implicit motor sequence learning.

We introduce the foot-stepping serial reaction time (SRT) task. This modified SRT task, complementing the classic SRT task that involves only finger-pressing movement, better approximates daily sequenced activities and allows researchers to study the dynamic processes underlying discrete response measures and disentangle the explicit process operating in implicit sequence learning.

This protocol describes a modified serial reaction time (SRT) task used to study implicit motor sequence learning. Unlike the classic SRT task that ...